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Topic Review (Newest First)

08-22-2012 12:05 PM

LakeArrowEd

Yep, it worked.

Quote:

Originally Posted by tubbedz

I don't know if this helps, but on my, TH350 automatic, 671 blown SBC, I would experience "detroit Roll" at idle. After many hours of double checked timing, gaskets, etc... I tried increasing the idle feed restriction jet on my billet metering blocks. Guess what happened....the surge went away. The blower was sucking my Holley, idle feed restriction dry. So I increased the restriction jet to allow more fuel at idle. Correct me if I am wrong, but this is just my own personal experience. I am not saying this is a cure-all modification, but just an example of unique situation that I ran into and wanted to share my experience with my fellow Hot Rodders. There maybe other factors or issues that are unique to your situation.

Exactly what worked for me. Super simple fix. Don't turn'em but a twitch or you'll run too lean. I run the boat at an altitude of 5K and running 91 pump fuel so I'd rather be a little rich. A roll of about 500-700RPM is okay, any more and it gets out of hand. The cam-roll/idle-roll in my case is a necessity rather than a "cool thing". I'd rather err on the safe side (rich). The motor you see in my pix is in my V-Drive, 22' Schiada Day Cruiser. 468 ci BBC with AFR 305 Alum Heads and other goodies.

03-10-2012 01:21 AM

2fox

Ithink this post was not for real she only has 3 post probably I Guy LOL
what girl would go throught that manuscript changes? BS.

03-09-2012 02:58 PM

68NovaSS

I'm thinking that was his point...

03-09-2012 02:31 PM

bigblockragtop

Some people are slow you never know.

03-09-2012 02:29 PM

malc

Original post was made on 09-14-2007, 07:23 AM.
Must have been sorted by now.

03-09-2012 02:11 PM

2fox

LOL Rachel not sure what I was trying to say.Iam better off without spell check
Do you what a was fringe to say? ??

03-09-2012 07:42 AM

bigblockragtop

That was a joke just a joke thought you might laugh. You know laffing is gud for u

03-09-2012 07:39 AM

2fox

Hell just forget a said anything what a fourm

03-08-2012 08:10 PM

bigblockragtop

and get Rachel can't wait to pull it out. giggitty you know someone had to go there

03-08-2012 07:47 PM

2fox

OK try to make this short as possible.I did have blower roll. But I just got it where its smooth as can be.in gear even got tci10"converter.
My set up is a BBC 489 TBS 8-71 750 mighty demons boost ref.to the bottom of the blower tee off into to vacuum / boost gauge.when floats where set to the highest point in the sight glass and mixture screws out 1.5 turns surged very bad not even in gear.
my fix was drop the sight glass level to middle. My 8 mixture sure are like .75 turns out.no surge at all no tachometer in car yet have not drive yet.
My combination is 489 eagle good stuff Srp blower flattops Heads are dart pro 1's.345cc intake runners with 2.30/1.90 valves. Msd 6alfor now w/6000 chip.timing set at 34°total and 16 intail. 2 inprimarys 3.5 collectors with 3.5 dynomax mufflers.came is comp can specs are? 255/262 @.050 appx lift is. 652 with 114lc
.in 68 SS chevelle tubbed with 9"rear. 3.50gears with Detroit locker 35 splines. I hope the gear is okay.? With my set up right not 13.5%OD.is 12psi boost. Of I swap pulleys around I got 12%UD and 6psi boost.
I'm.going to drop.the back down cause am on 93 pump gas with 15 gallon fuel cell with sender.
Any ?'pm me or post here

Need to mount seat.hook up throttle cable.bring toliet paper just in case. And get Rachel
Can't wait to pull it out

04-26-2009 04:28 PM

Jmark

My truck idles like that and I don't even have a blower! LOL

04-26-2009 04:10 PM

blown67SS

i have a blown SBC i purposely run blower surge because i like how it sounds but i can tune it out i get my motor to surge by running the idle a/f mix lean..heres a vid of what my car sounds like idling..

This is not a generic answer to a seemingly simple question.
I have had some that surge, some not. My fuel or alky motors did not. That being said, these are purpose built motors with one thing in mind. The idles on those motors are 1200- 1500 rpm respectively, (the 8 cylinder fuel burning engines idle at upwards of 2000 rpm) until they are fattened up just prior to take off.
My gasoline motors have surged at points depending on the jetting/metering setups being used but also rotor speed as well. My oldsmobile surged like hell but it never locked up the converter enough to make my head snap! My Liberator would surge a little but spinning a prop didn't realy translate into much jumping either. Over driven blowers will surge more than its underdriven counterparts. Again, depending on how much of what its being fed the surge may be minimal or drastic.
(is this getting anyone anywhere?)

I guess the missing parts to any equation here is engine size, supercharger size, air/fuel ratio, carburator CFM, pulley sizes and idle speeds. This would help in set-up and diagnostics.
Agree or disagree from the peanut gallery?

12-18-2008 07:37 PM

Tom Y

Resurrecting this discussion. I have a similar bad idle surge. Ford 3.8L V6, plenum style manifold, Weiand 144 and a Holly 700cfm blower carb. Its boost referenced to a port in the manifold under the blower. Idle surges wildly between 800-1500 RPM, great throttle response though. We have strong vacuum that surged with the idle surge from 18inches-12 inches. No vacuum leaks, good cranking compressiion in all 6 cylinders, we've been twisiting idle circuit screws, idle set screws, etc. We can't make the surge go away either.

Has anybody had any success correcting the surge?

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